Composites are well known dental restorative materials on the market. However, most of the organic based dental restoratives to date are based on methacrylate and/or acrylate chemistries. They usually cure via a light induced radical polymerization of unsaturated components. They often exhibit a very high stress upon curing due to the high polymerization shrinkage. It is thought that dental restorative materials based on oxirane chemistries may exhibit lower shrinkage and lower polymerization stress.
WO 98/47046 describes a photocurable, addition polymerizable composition which contains an epoxy resin and a photoinitiator system. The epoxy resin includes glycidyl ether monomers.
WO 00/19967 discloses a dental composition useful for making dental protheses or dental restoration comprising epoxy reactive functions which are polymerizable via a cationic cure process. The epoxy reactive functions include cycloaliphatic epoxides, glycidyl ether or oxetanes.
WO 98/22521 describes polymerizable substances containing an epoxide or a mixture of epoxides, a filler material, initiators, inhibitors and/or accelerators. The substances include cycloaliphatic epoxy functions with a relatively high viscosity.
WO 98/33645 describes a die adhesive or encapsulant of epoxy siloxane and polyepoxy resin. The polymerizable mixture contains a cycloaliphatic, epoxy-functional siloxane and a non-silicon-containing di-, tri- or polyepoxy resin. This resin, among others, may be a resin of diglycidyl ether of brominated bisphenol A.
WO 02/066535 discloses polymerizable preparations based on silicon compounds comprising aliphatic and cycloaliphatic epoxide groups. The preparations disclosed therein contain polymerizable compounds with at least one cycloaliphatic epoxide group per molecule.
A disadvantage of the dental composites known from the state of the art is that the polymerizable compounds based on glycidyl ethers are not very reactive in the polymerization reaction. A further drawback is, that some of the components of the dental composite materials form color during curing which is not desired for esthetic reasons. The formation of color can be measured on the cured composition using values on the L* a* b* scale. The a* and b* values, which represent the amount of red and yellow coloration, respectively, are particularly important values to indicate the esthetic properties of the cured dental compositions. The common dyes for dental compositions which can be added to the composition to correct the color if needed are yellow and red dyes. Thus, low a* and b* values are desired.
It is thus an object of the present invention to alleviate one or more of the problems mentioned above.
It is another object of the present invention to provide a composition with improved properties, especially higher reactivities of the epoxy moieties in cure reactions together with low color formation during curing.